Self-adaptive behavior is a feature which architects wants to include in their systems in order to improve its reliability. However, despite several ways to get it, it is still hard to implement a self-adaptive system which take in consideration quality attributes. Difficulties are related with architect's advanced knowledge in modelling, validating and implementing this kind of systems. In this paper we propose a model-driven architectural approach to allow the architect to define adaptation rules based on quality attributes enabling self-adaptive behavior in a SOA system.